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Abstract

This thesis addresses two distinct challenges in the galaxy formation and evolution theory. The first one is to accurately measure the dust attenuation. Understanding the global effects of dust on stellar light is crucial in deriving a number of galaxy physical properties. The second one is to explain how galaxies with the most massive halos remain passive. Models have implemented various feedback mechanisms to explain this phenomenon. Quiescence has been linked to the presence of radio-loud AGN through evidence gathered in the local universe. However, such observations were not feasible at high redshift up until recently. The first part of the thesis presents a novel approach to measure the attenuation of individual star forming galaxies at z ~ 0.8 based on deep optical LEGA-C survey spectra and multi-band photometry. A new attenuation curve modeling technique, and a new prescription for a typical attenuation curve of z ~ 0.8 galaxies are introduced. Using this technique, a large diversity among the main attenuation curve features (slope and UV bump strength) is observed, and the variation of those features with global galaxy properties is inspected. The main finding is that geometric effects dominate observed variations in attenuation. The second part of the thesis explores maintenance-mode feedback in quiescent galaxies through the incidence of radio-loud AGN, both in the local and high redshift (z ~ 1) universe. A high incidence rate of radio-loud AGN among round quiescent galaxies is observed, based on a z ~ 0.1 sample drawn from the SDSS/FIRST/NVSS surveys. On the other hand, radio-loud AGN are not seen among flat quiescent galaxies. This finding brings the general validity of the maintenance-mode feedback picture into question, as a different mechanism must be responsible for keeping these galaxies quiescent. This work is extended to z ~ 1 for a radio-loud AGN sample drawn from LEGA-C/VLA. The finding is that radio-loud AGN preferentially reside in galaxies with large stellar velocity dispersions, old stellar populations and round shapes but a larger sample is required to explore the dependence on flattening.